Posted by Tom-Anthony

In the Distilled R&D department we have been ramping up the amount of automated monitoring and analysis we do, with an internal system monitoring our client’s sites both directly and via various data sources to ensure they remain healthy and we are alerted to any problems that may arise.

Recently we started work to add in functionality for including the rel-alternate-hreflang annotations in this system. In this blog post I’m going to share an open-source Python library we’ve just started work on for the purpose, which makes it easy to read the hreflang entries from a page and identify errors with them.

If you’re not a Python aficionado then don’t despair, as I have also built a ready-to-go tool for you to use, which will quickly do some checks on the hreflang entries for any URL you specify. :)

Google’s Search Console (formerly Webmaster Tools) does have some basic rel-alternate-hreflang checking built in, but it is limited in how you can use it and you are restricted to using it for verified sites.

rel-alternate-hreflang checklist

Before we introduce the code, I wanted to quickly review a list of five easy and common mistakes that we will want to check for when looking at rel-alternate-hreflang annotations:

  • return tag errors – Every alternate language/locale URL of a page should, itself, include a link back to the first page. This makes sense but I’ve seen people make mistakes with it fairly often.
  • indirect / broken links – Links to alternate language/region versions of the page should no go via redirects, and should not link to missing or broken pages.
  • multiple entries – There should never be multiple entries for a single language/region combo.
  • multiple defaults – You should never have more than one x-default entry.
  • conflicting modes – rel-alternate-hreflang entries can be implemented via inline HTML, XML sitemaps, or HTTP headers. For any one set of pages only one implementation mode should be used.

So now imagine that we want to simply automate these checks quickly and simply…

Introducing: polly – the hreflang checker library

polly is the name for the library we have developed to help us solve this problem, and we are releasing it as open source so the SEO community can use it freely to build upon. We only started work on it last week, but we plan to continue developing it, and will also accept contributions to the code from the community, so we expect its feature set to grow rapidly.

If you are not comfortable tinkering with Python, then feel free to skip down to the next section of the post, where there is a tool that is built with polly which you can use right away.

Still here? Ok, great. You can install polly easily via pip:

pip install polly

You can then create a PollyPage() object which will do all our work and store the data simply by instantiating the class with the desired URL:

my_page = PollyPage("")

You can quickly see the hreflang entries on the page by running:

print my_page.alternate_urls_map

You can list all the hreflang values encountered on a page, and which countries and languages they cover:

print my_page.hreflang_values
print my_page.languages
print my_page.regions

You can also check various aspects of a page, see whether the pages it includes in its rel-alternate-hreflang entries point back, or whether there are entries that do not see retrievable (due to 404 or 500 etc. errors):

print my_page.is_default
print my_page.no_return_tag_pages()
print my_page.non_retrievable_pages()

Get more instructions and grab the code at the polly github page . Hit me up in the comments with any questions.

Free tool:

I have put together a very simple tool that uses polly to run some of the checks we highlighted above as being common mistakes with rel-alternate-hreflang, which you can visit right now and start using:

Simply enter a URL and hit enter, and you should see something like:

Example output from the ninja!

The tool shows you the rel-alternate-hreflang entries found on the page, the language and region of those entries, the alternate URLs, and any errors identified with the entry. It is perfect for doing quick’n’dirty checks of a URL to identify any errors.

As we add additional functionality to polly we will be updating as well, so please tweet me with feature ideas or suggestions.

To-do list!

This is the first release of polly and currently we only handle annotations that are in the HTML of the page, not those in the XML sitemap or HTTP headers. However, we are going to be updating polly (and over the coming weeks, so watch this space! :)


Here are a few links you may find helpful for hreflang:

Got suggestions?

With the increasing number of SEO directives and annotations available, and the ever-changing guidelines around how to deploy them, it is important to automate whatever areas possible. Hopefully polly is helpful to the community in this regard, and we want to here what ideas you have for making these tools more useful – here in the comments or via Twitter.

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